Recently, the on-line shopping through the Internet becomes quite familiar along with the spread of asymmetric digital subscriber line (ADSL), high-speed line such as optical fibers, and personal computers into the general households.
Internet shopping is convenient in that, by choosing a desired item from a wide variety of commodities while staying at home, the procedure can be easily proceeded from an order up to product reception. Meanwhile, considering from the vendor, there is no necessity to hold the actual store. Moreover, customers are widespread throughout the world.
However, in Internet shopping, the user is not allowed to make certain of a real product by his/her own eyes. For this reason, most vendor site describes a notice “Picture may differ from the real, please acknowledge” or the like. However, there are actually not a few complaints and returns of commodities from users. Accordingly, there is a desire for displaying a product image with a well texture feeling to a possible high extent on the user's display.
In the meanwhile, the display the user is using is in a size nearly 15 to 17 inches for a personal computer, and several inches for a PDA or cellular telephone.
The image processing techniques, for an image to be displayed on the user's display, include resolution conversion, reducing colors and format conversion, in conformity to the characteristic of the display as a destination of output.
Meanwhile, JP-A-2002-108757 describes an art that, taking account of a length-width ratio to put a content image on a low-resolution screen of a portable digital assistant, image conversion is carried out by rotating the image and further scaling down the same.
FIG. 1 is a diagram showing an arrangement of an image processing system in the prior art, which is to send and receive an image at between a server and a client. A client terminal 1 has a display unit 3, a resolution/color-number information database 4 and an information transmitting/receiving section 5. A server-type image processing apparatus 2 has a distributing section 6, an image database 7, a resolution converting unit 8, a color reducing converting unit 9 and a format converting unit 10. The both are connected together by the Internet or the like.
By the information transmitting/receiving section 5 of the client terminal 1, a signal requesting for an image to be desirably displayed on the display unit 3 is sent to the server-type image processing apparatus 2. At this time, simultaneously sent is the information about the resolution of and the number of displayable colors on the display unit 3. In the server-type image processing apparatus 2, the distributing section 6 receives the image request of from the information transmitting/receiving section 5 and reads out an image requested out of the images stored in the image database 7. The resolution converting unit 8 carries out a conversion as to the resolution and the height-width information about the image as requested to a size on the display unit 3. Meanwhile, the color reducing converting unit 9 makes a conversion to adapt the number of colors of the requested image to the colors displayable on the display unit 3. The format converting unit 10 converts the image into a format to be processed on the application software of the client terminal 1.
The image thus processed is sent from the distributing section 6 to the client terminal 1 where it is received by the information transmitting/receiving section 5 and then displayed on the display unit 3.
In the FIG. 1 arrangement, because the resolution converting unit 8 merely converts the image size into a size on the display unit 3, the product image is lost in sharpness due to resolution insufficiency. Thus, it is impossible to convey correctly the texture feeling of a product to the user. Particularly, there is a problem that it is quite difficult to know from the image a precise texture and material granular feeling of the product.
Consequently, in order to reproduce a high-resolution image on the low-resolution display unit 3, there is a need to carry out a sharpness enhancing process on the input image. Meanwhile, such deformation as appealing the user is required in order to convey the texture feeling of actual product over to the observer. Thus, deformation enhancing process is needed to carry out.
The conventional methods for improving the texture feeling include, for example, an unsharp mask to enhance image sharpness (see e.g. “Digital Image Technology III—Image Digital Processing in Printing (1)” by Hiroaki Kotera, pp 39-47, Japan Print Society Vol. 25, No. 3, 1988). The unsharp mask is a filter that the original image is first blurred to compute a differential between the blurred image and the original image, and the differential image is adjusted to further combine together the original image and the adjusted differential image thereby effecting a sharpness-increasing process.
However, concerning the unsharp mask for the conventional sharpness enhancing process, no considerations are made as to the direction in which sharpness is to enhance. Due to this, in the case the image acquired by an input device is deteriorated due to the affection of noise, the noise in certain cases is possibly made conspicuous.
FIG. 2A is a color distribution on an input image prepared by virtually adding noise to a texture image of a textile such as a sweater, shown in a color space represented by 8-bit digital data on each of pixel RGB colors. FIG. 2B is a color distribution of the input image of FIG. 2A increased in sharpness by means of an unsharp mask.
As shown in FIG. 2B, the sharpness enhancing process is problematically made noise more conspicuous than that prior to the sharpness enhancing process because of entire expansion of color distribution.
FIG. 3A shows a color distribution in RGB color space as a result of a principal components analysis on a low-resolution input image while FIG. 3B shows a color distribution in RGB color space as a result of a principal components analysis on a high-resolution input image. Here, the first primary component axis 1701 obtained as a result of principal components analysis is assumed as a direction of a color component of the input image.
From FIG. 3B, it can be seen that, concerning the image color distribution, the input image having a higher resolution has a distribution broader in the color component direction than that having a lower resolution, without extending in the other directions. Accordingly, as shown in FIG. 3B, it can be considered an ideal sharpness enhancing process to obtain the same color distribution as that raised in resolution.
Meanwhile, with the conventional unsharp mask, enhancing degree is controlled by weighting a high-frequency component in order to suppress against lightness variation and partial saturation occurrence. Also, the weighting value to a high-frequency component is determined empirically of enhancing processing, hence raising a problem the processing is complicate.
Meanwhile, in the case of computer graphics (CG), used are three-dimensional shape information and texture information to be mapped onto a shape. However, the texture in use is to be mapped without image-processing the texture of a subject. Due to this, there is a problem that, where the image is displayed on the display of a small-sized terminal unit, the texture is not easy to visually perceive because of insufficient resolution.
Also, in the case the resolution of display is secured, there encounters a problem that, when the subject is displayed in the entire by size-reduction, the texture is not easy to visually perceive because of resolution insufficiency.